"Software Engineering - A Layered Technology"
A Layered Technology Software Engineering Software Engineering tools methods process model a “quality” focus 1 A Common Process Framework Common process framework Framework activities work tasks work products milestones & deliverables QA checkpoints Umbrella Activities 2 Umbrella Activities Software project management Formal technical reviews Software quality assurance Software configuration management Document preparation and production Reusability management Measurement Risk management 3 The Process Model: Adaptability the framework activities will always be applied on every project ... BUT the tasks (and degree of rigor) for each activity will vary based on: the type of project (an “entry point” to the model) characteristics of the project common sense judgment; concurrence of the project team 4 Linear Models 5 Waterfall Model SSR - System Software Review PDR - Preliminary Design Review CDR - Critical Design Review TRR - Test Rediness Review FCA - Functional Configuration Audit PCA - Physical Configuration Audit Software ORR - Operational Rediness Review Requirements Analysis Software SRS Design Code and Unit SDS Testing Software Integration STP and Test Software SIP Acceptance Test SSR PDR CDR TRR FCA CRR PCA 6 Waterfall - DOD Model NASA Model) Hardware Hardware Implementation System Design Operational Software Requirements Timelines PP Analysis Preliminary Software SRS Design Detailed Software PDD Design Code and Unit SDS Testing Software Integration STP and Test Software SIP Acceptance Test SDR SSR PDR CDR TRR FCA PCA 7 Rapid Application Development Model Rapid Throwaway Prototype Model Software Requirements Analysis Build SRS Prototype PDD Software Design Code and Unit SDS Testing Software Integration STP and Test Software SIP Acceptance Test SSR PR PDR CDR TRR FCA CRR PCA 8 RAD Characteristics High speed adaptation of the linear model Based on Component-based construction Has incremental flavor Not well- suited where precision is required, e.g. high risk systems not easily modularized systems Have rigid performance requirements 1. Model the Information Flow 2. Refine the flows into Data elements 3. Model the data transformations 4. Generate the code 4GLs, component reuse, CASE 5. Test and integration 9 Reuse and Automated Development Models/Component Assembly Model Software Requirements Analysis Software SRS Design Code and Unit SDS Testing Software Integration STP and Test Software Acceptance SIP Test SSR PDR CDR TRR FCA CRR PCA Identify Reusable Components Informal Specification Formal Specifications Code 10 Component Based Development Architecture for Software Reuse Based on Object Orientation Classes are stored in a library When requirements are received,the first stop is the library 11 Linear Model Characteristics Documentation driven model systematic and requires rigor. Inflexible partitioning of project into distinct stages difficult to respond to changes in customer requirements Model appropriate when requirements are well-understood. Programmers HATE to create documentation. Users HATE to read documentation. If users read, they rarely understand documentation. Programmers don't understand other programmers documentations. Standards for documentation not clear although UML ordained. 12 Iterative Models Prototyping 13 Evolutionary (Prototype) Model ONLY A PART OF THE FULL SYSTEM Software Requirements Analysis Build SRS Prototype Software PDD Design Code and Unit Testing Software SDS Integration and Test Software STP Acceptance SIP Test SSR PR PDR CDR TRR FCA CRR PCA Series of Implementations of each PART 14 Evolutionary/Prototype Model Issues Process is not visible--Lack of process visibility Systems are often poorly structured—Change tends to corrupt the structures Special tools and techniques may be required—Special skills (e.g. in languages for rapid prototyping) may be required Applicability For small or medium-size interactive systems For parts of large systems (e.g. the user interface) For short-lifetime systems 15 Iterative Models team #3 team #2 b u s in e s s m o d e l in g team #1 b u s in e s s d a t a m o d e lin g m o d e l in g p r o c e s s business d a ta m o d e l in g modeling m o d e lin g a p p l i c a tio n g e n e r a t io n te s tin g & tu rn o v e r p ro cess data m o d e lin g modeling a p p lic a t io n g e n e ra tio n process modeling te s tin g & tu r n o v e r application generation testing & turnover 60 - 90 days RAD 16 The Incremental Model S steminform tion y / a increment 1 engineering analysis design code test delivery of 1st increment increment 2 analysis design code test delivery of 2nd increment increment 3nalysis a design code test delivery of 3rd increment increment 4 analysis design code test delivery of 4th incremen calendar time 17 Incremental Development Model ONLY A PART OF THE FULL SYSTEM Software Requirements Analysis Software SRS Design Code and Unit Testing Software SDS Integration STP and Test Software SIP Acceptance Test SSR PDR CDR TRR FCA CRR PCA Can Determine a PART at any phase. 18 Characteristics of Incremental Model Same Requirements, specification, maintenance,and requirement phases as in Waterfall The systems is partitioned into builds where each build is independently designed and scheduled "incrementally“ The 1st build gives some "production"functionality Subsequent builds add functionality User perspective Get some results quickly Reduces new system "culture shock" 19 Characteristics of Incremental Model Costs easily prorated over the development cycle It employs the systems approach Changes are easier to implement (e.g.design of later builds may not start until some phases are complete and all their changes well known). Problems - May degenerate into "Build and Fix“ May result in builds that cannot integrate with one another 20 Spiral Model Risk Planning Analysis Prototyping Simulation Client Operational Prototype Evaluation Verification for Next Level and Input Developing 21 An Evolutionary (Spiral) Model l Panning i i Rsk Analyss Prototyping Customer Communication n E gineering t Cus omer v E aluation t e e Cons ruction & R leas And Simulation/ Operational input Prototype/Verification for the Next Level/Development 22 CleanRoom Approach Specification Incremental Development Planning Specification and Design Usage Design Statistical Testing Certification 23 V Model Validate requirements OPERATION REQUIREMENTS & MAINTENANCE ANALYSIS ACCEPTANCE TESTING SYSTEM DESIGN SYSTEM Verify design TESTING PROGRAM UNIT & INTE- DESIGN GRATION TESTING CODING [Pfleeger 98] 24 Operational Specification Model [Pfleeger 98] Execute and Revise OPERATIONAL TRANSFORMED SPECIFICATION SPECIFICATION TEST (problem-oriented) (implementation- oriented) DELIVERED SYSTEM SYSTEM REQUIREMENTS (sometimes informal or incomplete) 25 Still Other Process Models Concurrent process model—recognizes that different part of the project will be at different places in the process Formal methods—the process to apply when a mathematical specification is to be developed 26 Formal Method Characteristics Formal Methods Model Specifications produce proofs Required rigorous notation Enhances accuracy Reduces flexibility Some Formal Methods Petri Nets, Zed, Hoare Logic, CSP, Weakest Preconditions Formal Methods Abstraction Add formality to reduce ambiguity Use graphical representations Describe the possible system states, transitions, and triggers 27 Capability Maturity Model Organizations are not born using a mature process model. Most organizations use NO known process model Watts Humphrey wrote a book to lay out a plan for improving the process model within organizations. His book “Managing the Software Process” and other research has greatly improved the software engineering process. The SEI Developed a capability maturity model which proposes a model for maturing an organizations process model. 28 Capability Maturity Model Five Process Maturity Levels Level 0: Chaos Level 1: Initial Level 2: Repeatable Level 3: Defined Level 4: Managed Level 5: Optimizing 29 Level 1: Initial The software process is characterized as ad hoc, and occasionally even chaotic. Few processes are defined, and success depends on individual effort. 30 Level 2: Repeatable Basic project management processes are established to track cost, schedule, and functionality. The necessary process discipline is in place to repeat earlier successes on projects with similar applications 31 Process Maturing to Level 2 Software configuration management Software quality assurance Software subcontract management Software project tracking and oversight Software project planning Requirement management 32 Level 3: Defined The software process for both management and engineering activities is documented, standardized, and integrated into an organization-wide software process. All projects use a documented and approved version of the organization’s process for developing and maintaining software. This level includes all characteristics defined for level 2. 33 Process Maturing Level 3 Peer Reviews Inter-group coordination Software product engineering Integrated software management Training program Organization process definition Organization process focus 34 Level 4: Managed Detailed measures of the software process and product quality are collected. Both the software process and products are quantitatively understood and controlled using detailed measures. This level includes all characteristics defined for level 3. 35 Process Maturing Level 4 Software quality management Quantitative process management 36 Level 5: Optimizing Continuous process improvement is enables by quantitative feedback from the process and from testing innovative ideas and technologies This level includes all characteristics defined for level 5. 37 Process Maturing Level 5 Process change management Technology change management Defect prevention 38 CMM Issues focuses on project management rather than product development. ignores the use of technologies such as rapid prototyping. does not incorporate risk analysis as a key process area does not define its domain of applicability 39